Driver fob variable resistors



Dec. 15, 1953 M. B. ARISMAN ErAL' Re. 23,750

DRIVER FOR VARIABLE RESISTORS Original Filed March 17, 1949 Marx/1n.ELArzsman .Adr'zdn .l Yaksvzk' uss'zz Reissued Dec. 15, 1953 DRIVER FORVARIABLE RESISTORS Mervin B. Arisman, Adrian J. Vaksvik, and Ralph W.Magnusen, Elkhart, vInd., assignors to Chicago Telephone SupplyCorporation, Elkhart, Ind., a corporation of Indiana Original No.2,484,667, dated October 11, 1949, Se-

rial NO. 81,872, March 17, 1949.

Application for reissue April 21, 1951, Serial No. 222,244

Matter enclosed in heavy brackets I: appears in the original patent butforms no part of this reissue specification; matter printed in italicsindicates the additions made by reissue.

7 Claims.

This invention relates to electrical control devices and refersparticularly to variable resistance controls of the type used in radioand television apparatus. The invention is advantageous in situationswhere two control devices are connected in tandem with the shaft of onehollow and having the shaft of the other rotatable therein.

In such control rotation of the shaft sweeps a contactor across the faceof a resistance element and to assure good electrical contact thecontactor generally comprises spring fingers maintained under tension.To place and maintain these spring fingers under tension entailssupporting the control shaft and, in fact, the entire rotating assemblyof the control, against inward or rearward thrust.

In conventional controls of this type the shaft has an annular groove inline with the front end of the bushing through which the shaft protrudesand a c washer is seated into this groove to bear against the front endof the bushing and thus hold the shaft against rearward axialdisplacement. In the case of tandem controls where one control shaftoperates within the other, this manner of holding the rotatable unitdriven by the hollow control shaft against rearward axial displacementcannot be used since the hollow shaft does not have sufficient wallthickness to permit an annular groove to be cut therein. This isespecially so in the very small controls recently developed for radioand television.

Consequently it has been the practice in the past to have the inner endof the hollow control shaft bear against the inner face of the cover ofits controi unit oragainst a hat-shaped washer supported thereon.However, the way in which the inner or rear 'end of the control shaftwas secured to the driver which carries the contactor always involvedears struck from the shaft and bent over the rear face of the driver sothat these ears constituted the rearmost portion of the rotatableassembly and perforce were the parts thereof which bore against and rodeon the cover wall or washer supported thereon. This construction lackedthe desired smoothness. Not only was the surface against which the earsbore inherently rough but since the ears were struck from portion of atube they were arcuate in cross section, even after they were bent over.Precautions were taken to flatten the ears as much as possible butnotwithstanding, the faces of the bent-over ears inevitably possessed adegree of concavity so that the actual contact with the wall of thecover was by the relatively sharp side edges of the ears.

Moreover, since the ears of necessity were relatively narrow, the thrustbearing formed by the engagement of the ears with the inner face of thecover or washer supported thereon was unstable and did notsatisfactorily hold the rotating structure against wobbling.

With these and other objections to past constructions in mind, it is anobject of the present invention to improve the end thrust bearing forthe rotating element of a variable resistance device through theutilization of a novel driver which in itself incorporates an annularrunner projecting rearwardly beyond the rearmost portion of the shaft tohave a smooth running contact over a substantial area with the innerface of the cover wall.

Another object of this invention is to provide a driver for variableresistors which incorporates within itself the carrier for thecontactor;a smooth annular thrust bearing surface, and rotation limiting stopabutments.

Still another object of this invention is to provide more accuratepositioning of the contactor with respect to the resistance element thanwas possible with the previous built-up construction of thecontactor-driver assembly in which the contactor was mounted on aninsulated drive arm which in turn was fixed to a stamped metal armsecured to the shaft and termed the stop arm since it carried the stopsfor limiting rotation of the shaft. With this built-up construction ofthe positioning of the contactor, and hence the magnitude of the contactpressure and to a large degree the smoothness of operation was affectedby several possible variables. The possible variations in the thicknessof the insulated drive arm, the metal stop arm and the hat shaped thrustwasher upon which the fastening ears rode, as well as the inevitablevariations in the flatness of the ears and any possible variations inthe thickness thereof all had an important bearing upon the accuracy ofthe positioning of the contactor.

The present invention eliminates these many variables affectingpositionin of the contactor by providing a driver which is molded in onepiece from suitable insulating material so that the contactor andoperating shaft may be attached directly thereto and the rotationlimiting abutments or stops formed as an integral part thereof. Thussince the possible variations in a molding are extremely slight the newconstruction assures uniform accuracy in the positioning of thecontactor not obtainable with past constructions.

With the above and other objects in view which will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed and more particularly defined by the appended claims, it beingunderstood that such changes in the precise embodiment of thehereindisclosed invention may be made as come within the scope of theclaims.

The accompanying drawing illustrates one complete example of thephysical embodiment of the invention constructed according to the bestmode so far devised for the practical application of the principlesthereof, and in which:

Figure 1 is a side view of a dual tandem variable resistance controlembodying this invention, parts thereof being broken away and insection;

Figure 2 is a perspective view of the driver of the front unit which hasthe hollow shaft, and the adjacent inner end of its shaft showndisassembled;

Figure 3 is a perspective view of the cup-shaped cover for this frontunit showing its flat irmer face against which the annular runner of thedriver abuts when the parts are assembled; and

Figure 4 is a perspective view of the assembled driver and shaft andillustrating the same from the front thereof to show the manner in whichthe contactor is mounted on the driver.

Referring now particularly to the accompanying drawing, the numerals 5and 6 designate the two units of a dual or tandem control of the type towhich this invention pertains. In use both units are mounted on [the] asupporting panel (not shown) by means of a single mounting sleeve 1.Each of the two units comprises a base 8 having an arcuate resistancestrip 9 and a collector ring I mounted on the inner face thereof. Theusual terminals extend from the ends of the resistance stri and thecollector ring.

A contactor indicated generally by the numeral ll overlies the innerface of the base to be advanced along the resistance strip to effect thedesired control function by rotation of a shaft journaled in the base.Spring contact fingers l2 and I3 on the contactor, respectively, bearagainst the resistance strip and the collector ring l0.

'As will be readily apparent the tension under which these springcontact fingers are maintained in the assembled condition of the controlunit imparts a rearward or inward thrust to the contactor rotatingassembly which, of course, must be opposed to retain the structureoperatively assembled.

In the case of the rearmost control device this requirement presents noserious problem since its rotating element is driven by a solid shaftit. Being solid, an annular c washer receiving groove is can be cut intothe shaft adjacent to the outer face of the base 8 or a spacing plate Itoverlying the same without objectionably weakening the shaft. Anordinary c washer il engaged in this groove bears against the spacingplate It to hold the shaft l4 and the parts mounted thereon againstinward axial displacement.

In the case of the front control 6, however, other means must beprovided to carry the inward thrust since its shaft It, being hollow torotatably receive the solid shaft, does not have suflicient wallthickness to permit cutting a c washer groove into it.

As noted hereinbefore, it was the practice in the past to utilize theend wall I! of the cupshaped cover 20 with which all control devices ofthis character are equipped to take the end thrust directly from thetubular shaft IS, the actual bearing being between outstruck ears on theend of the shaft by which the contactor driver was held to the shaft andthe inner face of the wall II or a hat-shaped washer overlying the same.This past construction precluded the attainment and maintenance of thesmooth operation necessary in controls of this kind. Even though specialprecautions were taken to flatten down the ears some degree of concavityinevitably remained and the resulting sharp side edges had a tendency tobite into the metal surface upon which the ears rode.

The present invention overcomes this objectionable characteristic ofpest constructions by obviating the exposed attaching ears through thesubstitution of a molded one piece contactor driver 2| for the built-upconstruction heretofore used. Though bent-over ears 22 are used to mountthe driver 2i on the tubular shaft [8, the ears are set down into acentral round recess 23 in the rear face of the driver. The cars 22 arethe endmost portions of diametrically opposite lugs 24 which projectfrom the shaft II and are seated in notches 25 in the wall of a hole 28axially through the driver. The hole 28 has substantially the samediameter as the bore of the hollow shaft It so as to form a continuationthereof for the smooth reception of the solid shaft ll.

Since the recess 23 is deeper than the thickness of the ears the edge ofthe wall defining the sides of the recess constitutes the rearmostportion of the driver and provides an annular runner 21 which lies in aplane normal to the shaft axis and rides directly on the inner face ofthe cover wall I9.

Being relatively large in diameter, this annular runner provides a largebearing for the molded driver and since the tubular shaft is rigidlysecured thereto this large bearing firmly holds the entire rotating unitagainst wobbling.

In addition to carrying the contactor and providing the rotating elementof the thrust bearing, the molded driver 2| also serves the function ofthe stop plate of past constructions and to this end has a lug 28integrally formed on its rear face. The sides of this lug provideabutments which coact with a stationary abutment formed by an instruckportion 36 on the cover at to limit rotation of the shaft.

From the foregoing description taken in connection with the accompanyingdrawing it will be readily apparent to those skilled in the art thatthis invention assures smooth operation in controls of the characterdescribed since the annular runner 21 can ride smoothly across the faceof the cover wall l9, and in all positions of rotation holds therotating elements firmly against wobbling, and that since the driver (ofwhich the runner 2'! is a part) is a molding, the contactor always willbe properly and accurately positioned with respect to the resistanceelement.

It will also be evident that while the invention is especially valuablein the case of tandem controls where one of the shafts of necessity is ahollow tube of relatively small wall thickness, it is equallysusceptible to use in controls which have solid shafts.

What we claim as our lnvention'is:

[1. In an electrical control device having a base provided with aresistance element and a bushing, and having a cup-shaped cover attachedto the base and coacting therewith to provide a housing: a shaftjournaled in the .bushing and Projecting into the housing; a driverfixed to the shaft at the end thereof inside the housing, said driverhaving an annular rearward projection concentric to the shaft with theextreme rear edge of said projection lying in a plane normal to theshaft axis and beyondthe adjacent end of the shaft so as to provide asmooth uninterrupted runner adapted to ride on and receive support fromthe bottom wall of the cup-shaped cover, whereby said runner and thebottom wall of the cup-shaped cover constitute a thrust bearing; and acontactor carried by the driver and interposed between the base and thedriver, said contactor having spring contact fingers to resiliently bearagainst the resistance element and by the spring tension thereof holdthe circular runner against the bottom of the cup-shaped cover] [2. Inan electrical control, the combination with a base having a bearing andan annular resistance element concentric therewith and exposed on theinner face of the base, and a cupshaped cover attached to the base andcoacting therewith to provide a housing enclosing said resistanceelement, of: a shaft journaled in the bearing and projecting into thehousing; a driver fixed to the shaft at the end thereof inside thehousing; a contactor carried by the driver and having a spring contactfinger to ride upon and resiliently bear against the resistance element;and an annular runner integral with the driver and extending rearwardlytherefrom, said runner being concentric to the control shaft and itsrearmost edge lying in a plane normal to the shaft axis and beyond theadjacent end of the shaft to ride upon and be supported by the innerface of the cup-shaped cover whereby said annular runner and the wall ofthe cover upon which it rides constitute a thrust bearing to hold theshaft and driver against inward displacement from a position maintainingthe spring contact finger under tension] [3. An electrical control ofthe type havingcooperating rotatable and stationary elements enclosedwithin a housing with the rotatable element movable by means of a shaftprotruding from one wall of the housing, characterized by the provisionof a thrust bearing comprising, the

wall of the housing opposite that through which the shaft protrudes; anda part on the shaft bearing against said rear wall, the part on theshaft which engages the rear wall being a smooth annular runnerconcentric to the shaft axis with its rearmost edge lying in a planeperpendicular to said shaft axis and extending beyond the rearmostportion of the shaft so as to have a smooth running bearing upon therear wall of the housing] [4. The electrical control set forth in claim3 further characterized by the fact that said part on the shaft is a onepiece molding of insulating material] [5. In an electrical resistancedevice: a base having a hole therethrough for the reception of a controlshaft; a resistance element on the inner face of the base; a controlshaft journaled in the hole in the base; a driver fixed to the shaft andoverlying the inner face of the base, a spring contactor mounted on thedriver and engaging the resistance element, the tension of the springcontactor imparting a rearward thrust to the driver and shaft; acup-shaped cover positioned over the rear face of the base and coactingwith the base to define a housing for the resistance element andcontactor; and a thrust bearingto oppose the rearward thrust engenderedupon the shaft and driver by the tension of the spring contactor, saidthrust bearing comprising, a ring integral with the driver andprojecting rearwardly therefrom beyond the rearmost portion of theshaft, the rear edge of said ring lying on a plane normal to the shaftaxis and having a smooth sliding engagement with the adjacent end wallof the cup-shaped cover] [6. The electrical resistance device of claim 5further characterized by the provision of cooperating stop abutments onthe driver and the cup-shaped cover to define the limits of rotation ofthe rotatable elements of the control] [7. In a variable resistancedevice of the type in which a resistance element is traversed by acontactor driven by a rotatable control shaft passing through a hole ina base of insulating material, and wherein the control shaft is biasedendwise toward the rear of the device: a cover attached to the base overthe rear face thereof, said cover coacting with the base to form ahousing for the device and having a wall substantially normal to the.shaft axis and opposite the rear end of the shaft; a driver for thecontactor fixed to the shaft inside the housing; and a circular runneron the rear of the driverextending beyond the rearmost portion of theshaft and throughout its entire circumference bearing against said wallof the cover to provide a smooth running thrust bearing for supportingthe shaft against the rearward end thrust thereon] [8. The variableresistance device of claim 7 further characterized by the provision ofcooperating stop abutments on the driver and the cover for limitingrotation of the driver and consequentl the contactor] 9. In a variableresistance device of the type in which a resistance element is traversedby a contactor driven by a rotatable control shaft passing through ahole in a base of insulating material, and wherein the control shaft isbiased endwisev toward the rear of the device: a cover attached to thebase and disposed over the rear face thereof, said cover having an endwall substantially normal to the shaft axis and in line with the rearend of the shaft; 2. driver for the contactor fixed to the shaft andsituated within the housing formed jointly by the cover and the base,said driver being a molding of insulating material and having a recessin its rear face, the side wall of said recess terminating in an annularrunner lying in a plane normal to the shaft axis, the front face of thedriver having a portion thereof abutting the end of the shaft and saiddriver having a hole therethrough coaxial with said runner with notchesin the wall of the hole; [ears extended] lugs extending longitudinallyfrom the shaft through the driver and into the recess at the rear facethereof, said [ears] lugs being seated in said notches and having theirfree end portions bent over the bottom of the reces to hold the driverto the shaft, said recess in the rear face of the driver being deeperthan the thickness of the [ears] bent over portions of the lugs so thatno portion of said [ears] lugs projects beyond the annular runner, andsaid runner bearing against the end wall of the cover and having asmooth sliding engagement therewith whereby the end wall of the coverand the runner coact to provide a thrust bearing for limiting rearwardendwise motion of the control shaft.

[10. The variable resistance device of claim 9 7 further characterizedby the fact that said annular recess in the rear face 01' the driver issubstantially larger in diameter than the diameter.

of the shaft so that the engagement of the annular runner defined by theside wall of the recess with the inner face of the cover extends over a.substantial area to firmly hold the shaft against wobbling] s 11. Thevariable resistance device of claim 9 wherein the control shaft isprovided with longitudinally extending lugs thereon passing through thedriver in line with the recessed portion thereof to drivingly connectthe shaft to the driver; and wherein the ears which hold the driver tothe shaft are formed on the rear emtremities of said lugs.

12. In an electrical control device having a base, a cup-shaped coverpositioned over one face of the base and coacting therewith to define ahousing, and a resistance element inside the housing on the inner faceof the base: a control shaft profecting through a hole in the base androtatably supported thereby with the rear end portion of the shaftinside the housing and the rearmost portions of the shaft terminating adistance forwardly of the end wall of the cover; a shoulder on the rearend portion of the control shaft lying between but spaced from the innerface of the base and the end wall of the cupshaped cover, and facing thelatter; a contactor cooperable with said resistance element; a driverwholly within the housing for driving said contactor, said driver havinga coaxial hole therethrough with notche in the wall of the hole; tonguesextending rearwardly from said shoulder on the control shaft and bentover at their rear extremities to mount the driver on the rear endportion of the control shaft for rotation therewith and with the driverclamped against said shoulder thereon and confined between said shoulderand the end wall of the cup-shaped cover so that the driver is supportedentirely by the control shaft; and a circular runner on the rear of thedriver extending beyond the rearmost portions of the control shaft butconcentric thereto, the rearmost edge of said runner lying in a planenormal to the shaft axis and bearing against the end wall of thecup-shaped cover to have smooth sliding engagement therewith, wherebythe end wall of the cover and the runner coact to provide a thrustbearing for limiting rearward endwise motion of the control shaft.

13. In an electrical control device having a base, a cup-shaped coverpositioned over one face of the base and coacting therewith to define -ahousing, and a stationary control element inside the housing on theinner face of the base: a control shaft projecting through a hole in thebase and rotatably supported thereby with the rear end portion of theshaft inside the housing and the rear extremity of the shaft terminatinga distance forwardly of the end wall of the cover; a shoulder on therear end portion of the shaft lying between but spaced from the innerface of the base and the end wall of the cover, and facing the latter; amovable control element in the housing overlying the inner face of thebase and cooperable with the stationary control element thereon; adriver wholly within the housing for driving said movable control,element; means mounting the driver on the rear end portion of thecontrol shaft, with the driver in juxtaposition to said shoulder on theshaft, including a hub portion on' the driver provided with a holetherethrough to receive the rear end till portion of the control shaft,lugs on the rear end portion of the control shaft engaged in notchesopening to the hole in the driver hub for connecting the driver to theshaft for rotation there- 7 rearwardly of the driver retaining means andengaged with the end wall of the cover to preclude contact of theretaining means therewith and to provide a thrust bearing for supportingthe control shaft against rearward end thrust thereon.

14. In an electrical control device of the type having cooperatingstationary and movable control elements contained within a housingprovided with spaced opposite front and rear end walls, with thestationary control element overlying and secured to the inner face ofthe front end wall: a control shaft profecting through a hole in thefront end wall and rotatably supported thereby with the rear end portionof the shaft inside the housing and the rear extremity of the shaftterminating a distance forwardly of the rear end wall of the housing; adriver wholly within the housing for driving the movable controlelement, said driver having a central portion providing a hub, and saidhub having a hole therethrough to receive the rear end portion of theshaft and provide for mounting the driver on the shaft; cooperatingmeans on the driver hub and the rear end portion of the shaft conprovide(1 thrust bearing 107' supporting the C011- trol shaft against rearwardend thrust thereon.

15. In an electrical control device of the tylw having cooperatingstationary and movable control elements contained within a housingprovided with spaced opposite front and rear end walls, with thestationary control element overlying and secured to the inner face ofthe front end wall: a control shaft projecting through a hole in thefront end wall and rotatably supported thereby with the rear end portionof the shaft inside the housing and having tongues extending rearwardlytherefrom and terminating a distance forwardly of the rear end wall ofthe housing; a driver wholly within the housing for driving the movablecontrol element, said driver having a central hole therethrough withnotches in the wall of said hole to receive said tongues on the shaftand provide for mounting the driver on the shaft, and having a centrallydisposed recess in its side opposite the rear end wall of the housing;an abutment on the rear end portion of the shaft overlying the frontside of the driver; an abutment on the rear extremity of each of saidtongues on the shaft overlying the rear side of the driver andcooperating with the first designated abutment to hold the driver on therear end portion of the shaft, said last named abutments lying whollywithin said recess in the rear of the driver; and runner means on thedriver spaced a distance rearwardly of said last abutments and engagedwith the rear end wall of the housing to preclude contact of said lastnamedv abutments therewith and to provide a thrust bearing forsupporting the control shaft against rearward end thrust thereon.

16. The electrical control device set forth in claim 15 wherein saidcontrol shalt has a coaxial uore of substantially uniform diameter nolarger than the central hole in the driver extending entirely throughthe shaft.

MERVIN B. ARISMAN. ADRIAN J. VAKSVIK. RALPH W. MAGNUSEN.

References Cited in the file of this patent 5 Number Number

